U.S. and European officials appeared ready to push for low-level sanctions against Iran like travel bans Thursday as country's president made clear he would not compromise on the day of a U.N. deadline.
Here's a timeline of the escalating crisis with Iran:
• Aug., 2002: Iranian exiles say that Tehran has built a vast uranium enrichment plant at Natanz and a heavy water plant at Arak without informing the United Nations.
• Sept., 2002: Construction work begins on Iran's first nuclear reactor at the Bushehr power plant.
• Dec., 2002: The existence of sites at Natanz and Arak is confirmed by satellite photographs shown on US television. The US accuses Tehran of "across-the-board pursuit of weapons of mass destruction". Iran agrees to inspections by the International Atomic Energy Authority (IAEA).
• Feb., 2003: Iranian President Mohammed Khatami reveals that Iran has unearthed uranium deposits and announces plans to develop a nuclear fuel cycle. IAEA chief Mohammed ElBaradei travels to Iran with a team of inspectors to begin probing Tehran's nuclear plans.
• June, 2003: Mr ElBaradei accuses Iran of not revealing the extent of its nuclear work, and urges leaders to sign up for more intrusive inspections.
• Aug., 2003: Traces of highly enriched weapons-grade uranium found at Natanz.
• Sept., 2003: More enriched uranium discovered, prompting urgent calls for Iran to sign a voluntary protocol formalizing a tougher inspection regime.
• Oct., 2003: After meeting French, German and U.K. foreign ministers, Tehran agrees to stop producing enriched uranium and formally decides to sign the Additional Protocol. No evidence is produced to confirm the end of enrichment.
• Nov., 2003: Mr ElBaradei says there is "no evidence" that Iran is pursuing nuclear weapons. The U.S. disagrees.
• Dec., 2003: Iran signs the protocol at the IAEA headquarters in Vienna.
• Feb., 2004: Abdul Qadeer Khan, the godfather of Pakistan's nuclear bomb, is reported to have sold Iran nuclear weapons technology.
IAEA report says Iran experimented with polonium-210, which can be used to trigger the chain reaction in a nuclear bomb. Iran did not explain the experiments. Iran again agrees to suspend enrichment, but again does not.
• March, 2004: Iran urged to reveal its entire nuclear program to the IAEA by 1 June 2004.
• June, 2004: Tehran is criticized by the IAEA for trying to import magnets for centrifuges and for not offering "full, timely and pro-active" co-operation with inspectors.
• Sept., 2004: IAEA orders Iran to stop preparations for a large-scale uranium enrichment. U.S. Secretary of State Colin Powell labels Iran a growing danger and calls for the U.N. Security Council to impose sanctions. Iran says it has resumed large-scale conversion of uranium ore into gas.
• Nov., 2004: Iran agrees to halt all enrichment activities during talks with the three European Union states, but pledges to resume in the future.
• Jan., 2005: IAEA inspectors allowed into the secretive Parchin plant near Tehran.
• April, 2005: Iran announces plans to resume uranium conversion at Isfahan.
• May, 2005: EU states warn that any resumption of conversion would end negotiations linked to trade and economic issues. Iran agrees to wait for detailed proposals from the Europeans at the end of July.
• Aug., 2005: Hardliner Mahmoud Ahmadinejad is installed as Iranian president, as Tehran pledges an "irreversible" resumption of enrichment.
Iran rejects the latest European proposals for resolving the nuclear crisis.
Iran appoints a hard-line politician, Ali Larijani, to lead the country's nuclear talks with the European Union.
Iran resumes sensitive fuel cycle work at its uranium conversion facility near the city of Isfahan.
An independent investigation finds no evidence that Iran was working on a secret nuclear weapons program. It concludes that traces of bomb-grade uranium in Iran's nuclear facilities came from contaminated Pakistani equipment, not Iranian activities. The U.S. dismisses the report.
• Sept., 2005: A study by the International Institute for Strategic Studies concludes that Iran is still several years away from acquiring a nuclear weapons capability.
Speaking before the U.N. General Assembly, Iranian President Mahmoud Ahmadinejad says his country has an "inalienable right" to produce nuclear fuel.
The IAEA passes a resolution setting Iran up for referral to the U.N. Security Council at a later date, on the grounds of Tehran's non-compliance with international nuclear safeguards.
• Nov. 11, 2005: Russia presents a plan, endorsed by the European Union and agreed to by the U.S., that would allow Iran to continue uranium enrichment but on Russian soil.
• Jan. 10, 2006: Iran removes U.N. seals at its Natanz uranium enrichment plant and resumes research on nuclear fuel on Tuesday, ignoring Western calls that it refrain from any work that could help it to develop atomic weapons.
• Jan. 12, 2006: Britain, France and Germany, who make up the EU-3, say the time has come for the U.N. Security Council to become involved and call for an emergency IAEA meeting next week.
• Jan. 13, 2006: Iran threatens to halt cooperation with the IAEA if it is referred to the Security Council. Bush says Iran's referral to the Council is the "logical" next step.
• Jan. 27, 2006: Bush voices public support for the Russian proposal. Iran rejects the Russian proposal as "not sufficient" for Iran's nuclear needs.
• Jan. 31, 2006: The five permanent members of the U.N. Security Council and Germany agree to report Iran to the council, postponing the action until March. IAEA reports that Iran has begun research relating to uranium enrichment, a step towards making nuclear weapons as well as fuel for reactors.
• Feb. 1, 2006: The five permanent Security Council members and Germany agree a draft resolution asking the IAEA to report Iran to the council. References to punitive measures are removed from the draft on Russia's request.
• Feb. 2, 2006: The IAEA's board of governors opens an emergency session on Iran. Russia and China promise Western powers to vote with them to refer Iran to the Security Council.
• Feb. 4, 2006: The International Atomic Energy Agency votes to report Iran to the U.N. Security Council over concerns that the country is trying to develop nuclear weapons.
• Feb. 5, 2006: Iran ends all voluntary cooperation with the IAEA, saying it would start uranium enrichment and bar surprise inspections of its facilities.
• Feb. 6, 2006: Applying economic sanctions on Iran without U.N. backing would be legitimate if other efforts fail to convince Tehran to halt uranium enrichment, says Principal Deputy Assistant Secretary of State Kurt Volker.
• Feb. 11, 2006: Iran warns it may reconsider nuclear Non-Proliferation Treaty membership.
• Feb. 13, 2006: Iran resumes some uranium-enrichment work at its Natanz nuclear plant, a first step in a process that can potentially yield either fuel for atomic reactors or bombs.
• Feb. 27, 2006: Negotiations between Iran and Russia on the Iranian nuclear program have made no significant progress despite talk of an outline agreement by both sides, the German and French foreign ministers say. The IAEA says that Iran appears determined to expand its uranium enrichment program.
• March 8, 2006: The IAEA discusses Iran's nuclear program. Iran threatens U.S. with "harm and pain" for its role in bringing the country before the U.N. Security Council.
• March 12, 2006: Iran says it is no longer considering a Russian compromise deal.
• March 20, 2006: Iranian President Mahmoud Ahmadinejad says Iran will stand by its right to obtain nuclear technology and anyone spreading propaganda against its atomic program will come to regret it.
• March 21, 2006: Iran's Supreme Leader Ayatollah Ali Khamenei sanctions talks with the United States on Iraq, saying Iranian officials would tell the U.S. to leave the country.
• March 22, 2006: Russia's foreign minister firmly rejects a draft U.N. Security Council statement aimed at pressuring Iran to stop enriching uranium, despite a new offer of amendments by Western powers.
• March 29, 2006: The U.N. Security Council unanimously approves a statement demanding that Iran suspend uranium enrichment.
• April 1, 2006: U.S. intelligence experts believe Iran would respond to U.S. military strikes on its nuclear sites by deploying its intelligence operatives and Hezbollah teams to carry out terrorist attacks worldwide, the Washington Post reports.
• April 2, 2006: Iran says it has successfully test fired a high-speed underwater missile capable of destroying warships and submarines.
• April 9, 2006: The New Yorker magazine reports that the administration is considering using tactical nuclear weapons against underground nuclear sites in Iran.
• April 10, 2006: Bush says force is not necessarily required to thwart Iran's nuclear ambitions and dismisses reports of plans for military strikes as "wild speculation."
• April 11, 2006: Iranian President Mahmoud Ahmadinejad says Iran has achieved the goal of enriching uranium for its nuclear power program and that the nation is determined to develop production on an industrial scale.
• April 14, 2006: Ahmadinejad again lashes out at Israel, saying it was "heading toward annihilation."
• April 16, 2006: Iran says it will give the Palestinian Authority $50 million in aid, moving in for the first time with money after the United States and Europe cut off funding to the Hamas-led government.
• April 16, 2006: The Sunday Times of London reports Iran has trained suicide bombers to attack British and American targets if Iran's nuclear sites are attacked.
• April 28, 2006: The IAEA says Iran has enriched uranium and persists with related activities in its nuclear program in defiance of the U.N. Security Council.
• April 29, 2006: Iran says it is willing to resume allowing snap U.N. atomic inspections if its case is dropped by the U.N. Security Council and passed back to the International Atomic Energy Agency.
• April 30, 2006: Secretary of State Condoleezza Rice says Iran's offer to let a watchdog agency inspect the country's nuclear facilities is a stalling tactic.
• May 2, 2006: An Iranian Revolutionary Guards commander says Israel would be Iran's first retaliatory target in response to any U.S. attack. European nations, backed by the U.S., outline a planned U.N. Security Council resolution to give "mandatory force" to the atomic watchdog agency's demands that Iran halt uranium enrichment.
• May 3, 2006: Britain and France introduce a U.N. Security Council resolution that would be legally binding and set the stage for sanctions against Iran if it does not abandon uranium enrichment.
• May 8, 2006: Iran's president writes to Bush, proposing what the nation's top nuclear negotiator called a new "diplomatic opening" between the two countries. The letter declares that liberalism and democracy had failed, and criticizes the United States over a host of issues ranging from the invasion of Iraq to its support for Israel. Secretary of State Rice dismisses the letter, saying it failed to resolve the dispute over the Iranian nuclear program.
• May 9, 2006: Representatives of the U.S., Russia, China, Britain and France as well as Germany agree to tell Iran the possible consequences of its refusal to halt its enrichment program and the benefits if it abandons it.
• May 10, 2006: Iran's president dismisses Western concerns over its nuclear program as "a big lie."
• May 14, 2006: Ahmadinejad says Iran would not accept any offer made by European states if it included a demand that Tehran stop what he called peaceful nuclear activities. The White House dismisses calls for direct talks with Iran to resolve the stand-off over its nuclear program, saying the United Nations was the best forum for those discussions.
• May 16, 2006: France, Germany and the U.K. say they plan to offer Iran a light-water nuclear reactor as part of a package of incentives.
• May 17, 2006: Ahmadinejad rules out halting nuclear fuel work in return for a package of EU incentives, saying the Europeans were offering "candy for gold."
• May 21, 2006: Sec. of State Rice says European powers have not asked the United States to provide security guarantees to Iran.
• May 31, 2006: In a major policy shift, the U.S. says it is prepared to join other nations in holding direct talks with Iran on its nuclear program if Iran first agrees to stop disputed nuclear activities.
• June 1, 2006: Six world powers — France, Britain, Germany, the United States, Russia and China — meet to discuss the crisis over Iran's nuclear program and reach an agreement on a package of incentives and penalties.
• June 2, 2006: The deputy head of Iran's Atomic Energy Organization says Iran will not stop its nuclear enrichment activities.
• June 3, 2006: Ahmadinejad says Iran will consider incentives from six world powers to persuade it to abandon plans to make nuclear fuel.
• June 5, 2006: European Union foreign policy chief Javier Solana will present Iran with a package of incentives on Tues., June 6, says a spokeswoman.
• June 7, 2006: A demand by the United States, France, Britain and Germany that Iran commit to a prolonged freeze on uranium enrichment has been softened to require only suspension during talks on an offer made by six countries.
• June 8, 2006: The IAEA says Iran slowed the pace of uranium enrichment over the past month but speeded up again on the day it received a package of incentives meant to persuade it to give up the technology.
• June 9, 2006: Top hard-line Iranian cleric Ayatollah Ahmad Jannati comes out against the Western incentive package.
• June 10, 2006: The Iranian foreign minister says Iran will make a counteroffer in response to the incentive package.
• June 11, 2006: Iran makes clear it wants changes in a Western incentives package aimed at making a breakthrough in the nuclear dispute, saying some parts should be thrown out and that the central issue of uranium enrichment needs clarification.
• June 13, 2006: The United States prohibits all transactions with four Chinese companies and one U.S. company for allegedly helping Iran acquire weapons of mass destruction and missiles capable of delivering them.
A statement drawn up by the 16-nation nonaligned bloc at the board meeting of the International Atomic Energy Agency backs Tehran, saying all countries have the right to pursue a nuclear program for civilian use.
• June 28, 2006: Secretary of State Condoleezza Rice joins international talks on Iran's nuclear program in Moscow.
• June 29, 2006: Iran's foreign minister brushes aside demands from the seven major industrialized nations and Russia to respond by July 5 to an international offer for Tehran to roll back its uranium enrichment program.
• July 3, 2006: The Bush administration warns Iran the United States would consider taking action in the United Nations if Tehran did not respond by July 12 to an offer designed to halt uranium enrichment.
• July 4, 2006: Russia and China press Iran to respond to an international package of incentives aimed ending the standoff over its nuclear program.
• July 5, 2006: Talks between Iran and the European Union on a package of incentives designed to defuse the standoff over Iran's atomic program are postponed. Rice warns Iran not to delay talks aimed at ending its nuclear program.
• July 9, 2006: Iran asks the International Atomic Energy Agency to remove Chris Charlier, who heads the inspection team probing Tehran's nuclear program.
• July 10, 2006: U.S. and British diplomats says Iran has had long enough to consider a proposed deal to give up disputed portions of its nuclear program.
• July 12, 2006: World powers agree to send Iran back to the United Nations Security Council for possible punishment.
• July 31, 2006: The U.N. Security Council passes a resolution giving Iran until Aug. 31 to suspend uranium enrichment or face the threat of economic and diplomatic sanctions. The resolution passes by a vote of 14-1. Qatar, which represents Arab states on the council, casts the lone dissenting vote.
• Aug. 22, 2006: Iran says it is ready for "serious negotiations" on its nuclear program, but a semiofficial news agency says the government is unwilling to abandon nuclear enrichment.
• Aug. 23, 2006: The U.S. says Iran's response falls short of the conditions set by the Security Council.
• Aug. 30, 2006: News Reports: Iran began enriching new batch of uranium, defying major powers as United Nations deadline comes closer
• Aug. 31, 2006: U.N. deadline for Iran to stop enriching uranium passes
(Sources: FOX News, BBC News, AP, Agence France Presse, Washington Post, Voice of America)